Karen M. Tobias, DVM, MS, DACVS
Professor, Small Animal Surgery, University of Tennessee College of Veterinary Medicine
Urinary tract surgeries can be challenging the first few times they are performed. Included below are descriptions of some of these surgeries, with some tips to make them easier and faster.
Renal biopsy: Obtained by blind percutaneous, keyhole, ultrasound guided percutaneous, or celiotomy approach. Vim Tru-Cut or modified Franklin-Silverman biopsy needle may be used. The needle should be directed across the cortex toward one of the renal poles (not the hilus) to prevent vascular, pelvic, or ureteral damage. Wedge biopsy of the outer parenchyma may also be used and will not affect renal function if more than 1/3 of the nephrons are functional. If a wedge is taken and the cortex must be closed to stop bleeding, temporarily occlude the arteries and let the parenchyma collapse before placing a cruciate suture across the capsule and cortex. Do not pull up on the suture or it will tear through. If bleeding persists, suture the omentum to the site.
Nephrotomy: Nephrotomy results temporarily (or permanently) in 20-50% decrease in renal function; thus bilateral nephrotomies should be "staged" as 2 operations at least 3 weeks apart.
The peritoneum is incised and the kidney is elevated out of its fossa. Temporary occlusion of the renal artery and vein provides hemostasis. A longitudinal midline incision is made through the capsule and the parenchyma; alternatively, the parenchyma is dissected bluntly to reach the renal pelvis and calyces. This exposure allows calculus removal. Culture the renal pelvis and flush the kidney with warm saline. Catheterize the ureter to check patency and flush (3.5 French red rubber catheter). The capsule is closed with a simple continuous pattern and then the parenchyma is compressed manually as flow is restored. Calculi may also be removed by pyelolithotomy if the renal pelvis and proximal ureter are dilated. Closure is with a simple continuous pattern of 5-0 or 6-0 absorbable suture.
Ureteral transplantation: The kidney can be elevated from its fossa and moved caudally to allow transplantation of the middle third of the ureter to the bladder or to a bladder flap. The ends of the ureters should be manipulated with sutures to prevent damage and tension at the anastomosis should be avoided. Ureters can be transplanted without opening the bladder, or by suturing mucosa directly through a ventral cystostomy. Extramural ectopic ureters are repaired with ureteral transplantation. A short oblique (3:1) submucosal tunnel is made during ureteral transplantation to decrease postoperative fibrosis and accelerate return of normal ureteral function. The ureteral mucosa is sutured to the bladder mucosa with simple interrupted sutures of 5-0 to 7-0 absorbable material. The distal bladder or urethral incision is closed with simple interrupted or continuous appositional sutures, since inverting may result in obstruction.
Antepubic cystostomy is used for urinary diversion when urethral catheterization is impossible or contraindicated. A purse string suture of PDS or Maxon is placed in the mid-body of the urinary bladder. A stab incision is made through the abdominal wall and the catheter is passed through. The catheter is then inserted through a bladder incision made in the center of the pursestring; the Foley bulb is inflated with sterile saline and the pursestring is tightened. The catheter is pulled up against the body wall, and the bladder is tacked in place. The catheter may be removed in 5-7 days. Urine leakage may continue from the stoma for 4 days after catheter removal. Use of antibiotics during the catheterization period does not prevent ascending infections; it is preferable to culture the catheter tip at the time of removal and then start antibiotics as needed.
Bladder rupture may be caused by abdominal trauma, urethral obstruction, or aggressive palpation or catheterization. Diagnosis is by abdominocentesis, contrast radiography, or exploratory laparotomy. Creatinine and potassium concentrations of abdominal fluid will be at least 1.7 and 1.4 times greater than serum concentrations, respectively. Surgery should always be delayed until the patient's potassium is no longer increased, the BUN and Creatinine are decreased to a reasonable level, and the patient is stable. During stabilization the abdomen can be drained with a closed catheter system. Serosal or omental patch grafting will provide extra support to the bladder if the tissues are friable or devitalized.
Scrotal urethrostomy: A permanent scrotal urethrostomy is performed in dogs when calculi or obstructions cannot be removed or because of stricture formation or calculus recurrence. The testicles and scrotum are excised and, if possible, the urethra is catheterized to assist identification and incision. The retractor penis is elevated and retracted, and a midline, 3-4 cm urethral incision is made. The urethral mucosa is sutured to the skin using fine monofilament nonabsorbable suture. Postoperatively sedation and physical restraint help limit self traumatization and hemorrhage. Complications include hemorrhage (72%) and stricture. Hemorrhage is seen especially during urination or excitation and lasts an average of 4.2 days; it often resolves after sedation or suture removal.
Perineal urethrostomy: Perineal urethrostomy is the surgical treatment of choice for unresolved, or frequent recurrence of, urethral obstruction in male cats. A pursestring suture placed in the anocutaneous junction helps prevent contamination of the surgical area. An elliptical incision is made around the scrotum and prepuce, and the penis is bluntly dissected to the level of the bulbourethral glands. The ischiocavernosus muscles and penile ligament must be transected to completely free the penis from its pelvic attachments. Minimal dorsal dissection should be performed, and ventral dissection should not extend cranial to the brim of the pubis. The retractor penis muscle is excised and the urethra is incised on its midline with iris scissors to the level of the bulbourethral glands. The final urethral diameter should be large enough to permit insertion of hemostats to their boxlocks. Urethral mucosa is sutured to skin with fine absorbable or nonabsorbable suture and the distal penis is ligated and amputated. Postoperative complications include stricture, hemorrhage, dysuria, self mutilation, dehiscence, tissue necrosis from urine leakage, and cystitis. Stricture is prevented by performing adequate dissection, avoiding urethral catheterization after surgery, and preventing postoperative traumatization (Elizabethan collar on the cat and shredded paper in litter box). Urine leakage is prevented by careful placement of proximal and distal sutures. Incontinence may occur if pelvic nerves are damaged during dissection. Bacterial cystitis is seen in 22-26% of cats with underlying uropathy after PU.
Urethral trauma: Urethral avulsions and ruptures are seen in 9% of dogs with pelvic trauma. Trauma may also occur secondary to compression injuries or urolithiasis. Urine leakage into subcutaneous tissues results in tissue necrosis; leakage into the abdomen results in uremia, hyperkalemia, dehydration, and abdominal distention. Rupture is treated with primary repair over an indwelling catheter, which remains in place for 3 to 7 days. More strictures are seen if trauma if ruptures are treated with indwelling catheterization without primary repair of a rupture, or primary repair without indwelling catheterization. Indwelling urethral catheters can damage urethral epithelium. Repair should be delayed if severe tissue trauma is present; urinary diversion will be necessary to maintain the animal until surgery and to prevent delayed healing from urine leakage after surgery. If incomplete urethral rupture has occurred and a segment of mucosa bridges the defect, a urethral catheter may be placed to splint the area until healing and regeneration occur. Stricture formation occurs if no mucosal bridge is present.